What fungicides are effective for controlling potato late blight?
What harm does potato late blight cause? What fungicides are used to control potato late blight? We also ask experienced growers to help explain. Potato late blight is a major disease in potato-growing areas, and it occurs rather severely in winter potato-growing areas. The disease damages leaves, petioles, stems and tubers, causing considerable losses in production. Because...
What harm does potato late blight cause? What fungicides are used to control potato late blight? We also ask experienced growers to help explainPotato late blight is a major disease in potato-growing areas, and it occurs rather severely in winter potato-growing areas. The disease damages leaves, petioles, stems and tubers, causing considerable losses in production. Therefore Zhongdi Network has compiled the harm caused by potato late blight and its control methods, listed below for growers' reference.
The harm caused by potato late blight:
On potatoes affected by late blight, dark green small spots first appear at the leaf tips and leaf margins. Under moist conditions favorable for the disease, the spots rapidly expand into water-soaked, irregular dark green lesions; the edges of the diseased leaves curl upward and dry out, and on the underside of the leaves a downy mildew layer formed by the pathogen can be seen along the edges of the lesions.
When potato late blight is severe, the lesions spread to the veins, petioles and stems, and the diseased leaves wither and drop off. On infected tubers, small brown spots first appear, which later enlarge into sunken, dark brown irregular lesions. When a diseased tuber is cut open, a layer of brownish dried tissue can be seen.
The potato late blight pathogen mainly overwinters in the tubers. After planting, it invades the stems and leaves as the young sprouts grow, and the pathogen spreads and infects further through air and water flow. Rainy, foggy and dewy weather is favorable for the disease. It is most likely to become epidemic at a temperature of around 20°C and high humidity.
Control methods for potato late blight:
Method one,Before sowing potatoes, select seed tubers strictly, remove diseased and rotten tubers, and use healthy, disease-free seed potatoes. In concentrated production areas, disease-free seed potato bases should be established to provide farmers with disease-free, healthy seed potatoes.
Method two,Disinfect the potato seed tubers. Spread the seed tubers out, then for each mu of seed potatoes use 5 grams of 58% metalaxyl-mancozeb wettable powder mixed with 2.5 kg of water and spray evenly over the seed tubers. After drying in the shade, they can be sown.
Method three,Plant potatoes at a reasonable density. In low-lying, rain-rich planting areas, timely drainage can reduce the spread of the pathogen.
Method four,Remove diseased potato leaves promptly and carry out chemical control. At the early stage of the disease, remove the diseased leaves at the center of infection, and use metalaxyl-mancozeb or the broad-spectrum fungicide carbendazim for 1-3 applications.
Method five,Late blight is highly epidemic, so the control strategy should be based on early control. When conditions for the disease appear, spray in advance for prevention.
Fungicide options: 25% metalaxyl wettable powder at 500 times dilution, or 58% metalaxyl-mancozeb wettable powder at 500-600 times dilution, or 40% fosetyl-aluminium wettable powder at 300 times dilution, or 70% mancozeb wettable powder at 800 times dilution, or 50% anilazine wettable powder at 500 times dilution, or 50% thiram wettable powder at 500 times dilution, or 64% oxadixyl-mancozeb wettable powder at 500 times dilution, or 60% iprobenfos-fosetyl-aluminium wettable powder at 500 times dilution, or 72% cymoxanil wettable powder at 700-800 times dilution, or 69% dimethomorph-mancozeb wettable powder at 1000 times dilution, or 72.2% propamocarb aqueous solution at 800 times dilution, or Bordeaux mixture at 1:1:200. Spray once every 7-10 days, and 2-3 sprays are sufficient. To slow the development of resistance, attention should be paid to rotating the fungicides.
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